Why the same face may look male or female

Published: Thursday, November 25, 2010, 14:00 [IST]

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Washington, Nov 25 (ANI): Neuroscientists have discovered that our brains apparently can perceive some faces as male when it appears in one section of our field of view, but female when it appears in another.

The finding, by the experts at Harvard University and Massachusetts Institute of Technology, challenges the longstanding tenet of neuroscience that how the brain sees an object should not depend on where the object is located relative to the observer.

"It's the kind of thing you would not predict - that you would look at two identical faces and think they look different," said Arash Afraz, a postdoctoral associate at MIT's McGovern Institute for Brain Research and lead author of the study.

Under normal conditions, the brain's inconsistency in arriving at a gender judgement is not noticeable because it assembles many other clues like hair and clothing.

However, Afraz and the other scientists found that something different occurs when we view computer-generated faces - A pattern of biases, based on location of the face, emerges.

They showed test participants a random series of faces ranging from 'very male' to 'very female' and asked them to classify the gender of each face.

For more androgynous-looking faces, the participants rated the same faces as male or female, depending on where they appeared.

The researchers found that different people had different patterns of bias in their perception of male and female. For example, some people always judged androgynous faces to be female when the faces appeared in the upper right corner of their vision. Others assessing the same faces in the same section of their vision judged the faces to be male.

The participants also showed biases when judging the age of faces, but the pattern for age bias was independent from the pattern for gender bias in each individual.

The researchers believe that a relatively small number of neurons in the visual cortex - the part of the brain where images are processed - does the job of interpreting the gender of faces.

The smaller the image, the fewer cells are activated, so cells that respond to female faces may dominate. In a different part of the visual cortex, cells that respond to male faces may dominate.

The findings are published in the November 24 online edition of the journal Current Biology. (ANI)